Omnidirectional antenna



y 4, 1954 w. SICHAK 2,677,767

' OMNIDIRECTIONAL ANTENNA Filed June 4, 1949 INVENTOR I WILL/AM S/CHA/f ATTORNEY Patented May 4, 1954 OMNIDIRECTIONAL ANTENNA William Siohak, Lyndhurst, N. J assignor to International Standard Electric Corporation, New York, N. Y., a. corporation of Delaware Application June 4, 1949, Serial No. 97,233

4 Claims.

This invention relates to radio antennas, and more particularly to antennas for use at very high frequencies and of the omni-directional type.

A principal object of the invention is to provide an omni-directional high-gain antenna for use at very high frequencies.

Heretofore the usual method of achieving high gain in omni-directional high frequency radio antennas has been to provide a series of similar radiators which are mounted in a stacked-up array. These prior arrangements therefore require a very careful design of the feed line and supporting masts or columns for the series of radiators, and as a result, the cost and installation difficulties are considerable.

The present invention has for one of its principal objects the provision of a high-gain omnidirectional antenna using only a single radiator which is symmetrically mounted with respect to a plurality of metallic members arranged as a lens for electromagnetic waves to focus the radiation efficiently with the desired directivity while maintaining the desired omni-directional field pattern.

A feature of the invention relates to an antenna having a single radiator, preferably in the form of a loop, which is located between a pair of opposed conductive cones and surrounded by a series of annularmetal discs which act as a lens 7 to focus the radiated waves in the desired omnidirectional field pattern.

Another feature relates to a simplified and rugged construction of high frequency antenna for producing horizontally polarized waves.

Another feature relates to an omni-directional high-gain antenna employing a single radiator with associated reflectors and electromagnetic wave lens means, and which can be readily matched to a feed line for operation over a predetermined frequency band. As a result of this feature, only one transmission line is used to feed the radiator, thus avoiding the use of a large number of feed cables and a correspondingly large junction box, as is the case With a stackedup array of radiators.

The above-mentioned and other features and objects of this invention and the manner of attaining them will become more apparent and the invention itself will be best understood, by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein:

Fig. 1 is a vertical elevational and sectional view of an antenna according to the invention.

can be rigidly fastened to a metal supporting rod 9. Conductor I0 is the central or inner conductor of a coaxial transmission or feed line H which insulatingly passes through an outer or pipe'conductor l2, which pipe conductor can also serve as the supporting rod 9 for the antenna. Inner conductor I0 is connected to each of the circular segments 2-4 by a screw I 3 extending through apertures in supporting rod 9. Suitably fastened to the end of pipe [2 is a' metal cone M whosebase has a flange l5 fastened by bolts IE to a circular metal plate [1. Fastened to the upper end of rod 9is an inverted metal cone [8 whose base has a flange l9 fastened by bolts 20 to another circular metal plate 2|. The cones l4 and [8 are of the same dimensions and the loop I is equally spaced from'the opposing truncated apices of the cones and preferably with the plane of the loop perpendicularto the cone axes.

Surrounding the loop and cones, is an upper series of annular metal discs 22-24, and a corresponding lower series of similar discs 25-21. While the drawing sh'ows each series comprised of three discs, it will be understood that a greater or less number can be employed consistent with the focussing and directing characteristics desired. The discs of each series have central openings each of different diameter. The discs closer to the base of each cone have smaller openings, and the openings of successive cones are of increasing diameter, as shown in the drawing. Thus the inner edges of the disc openings will be located on a surface of revolution represented by the dotted lines.

In order to maintain the discs accurately spaced and in the desired parallelism, they have a series of aligned apertures through which pass the brass rods 28. Fitted over each rod, so as to be located between respective discs, are tubular brass spacers 29. The spacers are of different lengths in accordance with the desired spacing between the respective annular discs. The opposite ends of each rod 28 are threaded to receive suitable fastening nuts 30. The discs 22-21 are dimensioned as regards their central openings and their relative spacings, so as to act as a focussing lens for the waves radiated directly from loop I, as well as for the waves radiated 3 from the loop which are reflected from the cones l4 and I8. The end plates 17 and 2| are solid, and form eifective conductive continuations of the bases of the respective cones, thus insuring that all the power radiated by loop I goes through the lens formed by discs 22-21. Thus the field pattern of the radiated waves is omni-directional and circularly polarized.

While the height h and diameter d are not critical, it has been found that the height it should not be materially more than three-quarters of the diameter (1, otherwise substantial reduction in the efficient operating frequency band width of the antenna is encountered. It has also been found that the feed impedance oi the antenna as a whole, is not much different from the impedance of the loop I alone. In one particular construction designed to operate in the frequency band 2,000 to 3,000 megacycles per second, the height h was approximately 26 inches and the diameter d was approximately 35 inches; the discs 24, 25, were spaced approximately 6.25 inches apart; the discs 25, 25, were spaced approximately 3.13 inches apart, as were the discs 26 and 27; the spacing between disc 2": and plate H was approximately 3.77 inches. Similarly the spacing between discs 23 and 24 was approximately 313 inches, as was the spacing between the discs 22 and 23; and the spacing between disc 22 and plate 2! was approximately inches. The cones I4 and 18 had their truncated apex ends with a diameter approximately 1% inches and their larger or base ends of approximately 11 inches with the spacing s between the truncated apices of approximately 4 inches. In this particular antenna, the discs 24 and 25 had openings of approximately 34 inches in diameter, the discs 23 and 26 had openings of approximately 29 inches in diameter, and the discs 22 and 27 had openings of approximately 28 inches in diameter, the taper of the cones i4 and 48 being at an angle of approximately 45 degrees. In any event, the general relation between the spacings of the discs and their respective openings were designed in accordance with the gen-- eral principles of lens design.

While I have described above the principles of my invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not a limitation to the scope of my invention.

What is claimed is:

1. An antenna comprising a single omnidirectional radiator element, a pair of conical reflectors between the opposed apices of which said element is mounted, a pair of spaced parallel metal end plates between which said reflectors are mounted, and a plurality of spaced annular metal discs symmetrically surrounding said reflectors and said radiator.

2. An antenna according to claim 1 in which said annular metal discs have their annular openings of respectively different diameter and the discs being spaced apart relatively from each other to form an electromagnetic wave lens symmetrically surrounding said radiator and reflectors.

3. An antenna comprising a pair of spaced metal end plates, a plurality of tie rods extend ing between said plates, a plurality of annular metal discs in spaced parallelism between said end plates, spacer means for maintaining said discs in fixed spaced relation, a conductive conical member having its base attached to one end plate, another conical conductive member having its base attached to the other end plate, said conical members being in substantial axial alignment and with their apices spaced apart, and a single omnidirectional radiator element mounted symmetrically between said apices.

4. An antenna according to claim 3 in which said discs have their apertures respectively or" reasing diameter, with the smaller aperturcd discs being located adjacent the bases of the respective conical members and with the larger apcrtured discs located adjacent the apices of the 'espective conical members.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Proc. IRE, vol. 34-, pages 828-836, November 194.6, 25033.63. 

